The present invention relates to a process for producing an olefin polymer by the use of a novel solid catalyst component. More particularly, the present invention relates to a process for producing a polymer of an .alpha.-olefin such as ethylene, propylene, butene-1, 4-methylpentene-1, and 3-methylbutene-1, particularly a polymer of an .alpha.-olefin having not less than three carbon atoms by the use of a catalyst which comprises a novel catalyst component supported on a carrier, an organometalic compound of a metal of Group I, II or III of the Periodic Table, and an electron donating compound. The catalyst used in the process of the present invention is excellent in polymerization activity and stereospecificity, shows a very slight lowering in polymerization activity and stereospecificity during a long-term polymerization, and is capable of producing a polymer having an excellent particle property.
Many proposals have been heretofore made regarding the production of a catalyst having a high activity and capable of producing a polymer of high stereospecificity from an .alpha.-olefin of at least three carbon atoms. Most of the catalysts thus proposed are not fully satisfactory in terms of polymerization activity and stereospecificity and also in particle property of the produced polymer. Further improvement, therefore, in catalyst has been desired.
The present inventors have already proposed in Japanese Patent Application Laid-Open (KOKAI) No. 64-54007(1989), a for producing a catalyst excellent in polymerization activity and stereospecificity, and capable of forming a polymer excellent in particle property, which process comprises preparing a solid catalyst component obtained by contact treatment of the reaction product of a magnesium alkoxide, a titanium alkoxide and a silicon alkoxide with a halogen-containing titanium compound and an electron donating compound and combining the solid catalyst component with an organometalic compound of a metal of Group I, II or III of Periodic Table, and optionally an electron donating compound. This catalyst, however, has a disadvantage that it causes a serious lowering of polymerization activity during a long-term polymerization (3-hour polymerization, for example). A large lowering in polymerization activity during a long-term polymerization brings about a low productivity in a process requiring a long-term polymerization condition.
In the circumstances described above, the present inventors have made a continuous study for providing a process for producing an olefin polymer by the use of a novel catalyst system excellent in polymerization activity and stereospecificity, showing a very slight lowering in polymerization activity and stereospecificity during a long-term polymerization, and capable of forming an olefin polymer excellent in particle property, and as the results, have found a solid catalyst component which meets the purpose. The present invention has been accomplished based on this finding.